A faith healer with astonishing efficacy, but no accompanying explanation or metaphysics.

At the age of 34 he was suddenly overwhelmed with the conviction that he had the gift of curing scrofula. This impulse become so strong that he was compiled to stroke several victims and, in fact, did cure them.

Three years later, there was a fever epidemic. He become convinced that he could cure that as well and, in fact, cured all who came to him.

A few months later, he realized he could heal wounds and ulcers, as well as convulsions, dropsy, and much else. Greatrakes cured a former Commonwealth Governor of an acute ague in just a few minutes. In 1666 went to England and ministered to the masses in London.

Charles Mackay (1841) said of Greatrakes,

Mr. Valentine Greatraks, who, without mentioning magnetism, or laying claim to any theory, practised upon himself and others a deception much more akin to the animal magnetism of the present day than the mineral magnetism it was then so much the fashion to study.